Background and aims: EMG biofeedback as a relatively new tool in helping to relieve muscle dysfunction has been proposed. The aim of this study was to investigate the effects of a strengthening exercise program with electromyographical biofeedback on the alignment corrections of the patella and the knee pain in patients with patella-femoral pain syndrome.Methods: This research was a clinical trials study. 22 participants with patella-femoral pain syndrome were randomly divided into two equal groups (n=11). The first group underwent a strengthening exercise program with biofeedback electromyography. The second group also recieved a strengthening exercise program without biofeedback electromyography. Using VAS questionnaire, the knee pain was assessed. Radiography technique was also applied to evaluate the knee alignments including Sulcus, congruence and tilt angles and Q angle assessed by clinical tests. Pair t-test and Independent t-test with SPSS were used for statistical analysis.Results: The results showed that the knee pain, congruence and Q angle had significant decrease after the therapy in both groups (P<0.05). However, the patellar tilt displayed a significant decrease only in the strengthening exercise program in the biofeedback electromyography group (P<0.05). In between group comparisons, pain and Q angle reduction after strengthening exercise program with biofeedback electromyography group was significantly more than strengthening exercise program without biofeedback electromyography group (P<0.05).Conclusion: Muscular strengthening exercise with electromyographical biofeedback displayed a better treatment outcome for pain reduction and correction of knee alignment. It seems that the provision of electromyographic biofeedback be preferred in comparison with the muscular strength training method without electromyographic biofeedback by creating more motivation for performing the exercises precisely and it can be used as a supportive tool in rehabilitation.